Didn't she also say on twitter that this scene was another first for her? 'Cause ever since reading that, and can't keep my mind of thinking she shot a DP scene.
Based on the still photos a few posts up from this one, it doesn't appear to be a DP scene. It looks like it could be Nikki's first anal creampie scene (she did her first vaginal creampie a few months ago for BangBros).